Electeomagnetic device



Feb. 20, 1923.

E. R. CARICHOFF ET AL.

ELECTROMAGNETIC DEVICE. I

FILED NOV. 2, I920.

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Inventor-'1 Eluger e R. Car-Ichoff Beqja 'ri 'W by Jone s 12% Their Attor 'neyi 20, 1923-. 1,445,994. w i E- R- CARICHOFF ET AL.

ELECTROMAG NETIC DEVICE.

FILED NOV. 2, 1920. 2 SHEET$-SHEET 2.

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Patented Feb. 20, 1923.

.UNITED STATES j "1,445,994 PATENT OFFICEQ EUGENE E. CARICHOFF AND BENJAMIN w. JoNEs, E scrrENE'e'rAnn-YNEw YORK, ASSIGNORS T0 GENERAL ELECTRIC COMPANY, A CORPORATION on NEW YORK.

ELECTROMAGNETIC DEVICE.

Application filed Novembcr2, 1920. Serial No. 421,290.

To all 10 item it may concern Be it known that we, EUG sNE R. CAnIcH- orr and BENJAMIN WV. JoNEs, citizens of the United States, residin at Schenectady,

county of Schenectady, tate of New York,

have invented certain new and useful Improvements in Electromagnetic Devices, of which the following is a specification.

Our invention relates to improvements in electromagnetic devices, and in particular to improvements in electromagnetic switches of the series lock-out type having shunt controlling coils.

The operating range of the ordinary electromagnetic switch of the type which is magnetically held open until the current inits operating winding is reduced to a predetermined value and is then closed magnetically and held closed magnetically-a series lock-0ut switchis between the calibrating value, the maximum value of current at which the switch will close, and a certain lower value. In certain switches this lower value is approximately 30 per cent of the full load capacity of the winding. At any point between this 30 per cent and the calibrating value the switch will close, but it will not close at any value below the 30 per cent. Thus, for instance, if the switch is used to short circuit a resistor in the armature circuit of a motor, if the load on the motor is such that the current through the series winding ofthe switch is less than 230 per cent of the capacity of the winding of the switch, the switch will not close and the resistor will remain in the motor armature circuit. If the load on the motor is suddenly increased, the motor speed will momentarily drop due to the voltage drop.

through the resistance, and then when the current value is such that the switch will close, the short circuiting of the resistor will cause the motor speed to be increased. This fluctuation in the motor speed is objectionable, and one of the objects of our invention is to provide a switchwhich does not have this inherent objection for the particular instance cited and other objections oflike nature. In accordance with our invention, the switch will close at any value of current below the look-out or calibrating value including zero value.

Furthermore, the usual series lock-out contactor has theobjectionable feature that if the contartor is closed and the current in the series winding is reversed, the contactor will open, and if the current in the reverse direction is between the calibrating value,-' and theSO per cent value, the contactorwill reclose. Reverse current protective devices generally have this objectionable feature of operating in response to a-reversal of current and then reclosing. One of the ob ects of our 'inventlon is to provide an electromagnetic switch whichwill open in response to a reversal of current and remain open as long as the reverse current persists and not reclose at any value of current in the re verse direction. In part1cular,one of the objects ofour invention is to provide a series lock-out switch which will be free from the objectionable feature above pointed out.

In carrying our invention into effect in one form, we provide an electromagneticdevice of the series lock-out type with a shunt controlling winding and arrange the magnetic circuits so that the device will have the desirable features above pointed out and other desirable features which will be apparent from an understanding of the invention.

For a better understanding of: our inven .tion,-reference ishad to the accompanying drawings, which show an embodiment ofthe invention in an electromagnetic switch for purposes of explanation, and in which Fig. 1 shows a side viewof an electromagnetic switch of the series lock-out type with a shunt controlling winding; Fig. 2 is :aplan view ofthe same; Fig. 3'is' a detail showing the closing and holding-open air gaps and certain features of the arrangement of the magnetic circuits; Fig. 4 is a simplified diagram of a motor control system embodying the invention; and Fig. 5 shows curves whioh'help to an understanding of the invention. i w

Referring to the drawings, the switch mechanism is mounted ona ba'se-lOof slate or other suitable insulating material, and the movable switch member 11 in theform of a bell cranklever is pivoted at 12 to the member 13 which is a. part oftlie magnetic structure of the switch. The wiping contact finger 14: is pivotally mountedon the bell crank switch member ll at 15, and a spring 16 is provided for the purpose of resiliently mounting the contact 14: so that the contact 1 will make a wiping engageing, and when the contac'toris closed there will be a spring pressure between the con tacts. The bell crank 11 is pivotally connected at 18 to a plunger [19 which constitutes the movable member of the magnetic structure of the switch. This plunger 19 is constructed substantially as shown in Fig. 3 with a lower port-ion 20 of reduced cross-sectional area. A sleeve 21 of brass or other non-magnetic material surrounds the lower end 20 of reduced cross-section for the purpose of preventing the plunger from sticking to the adjustable sleeve 22 of magnetic material which surrounds the end .20 and the sleeve 21. This adjustable sleeve 22 is preferably in the form of a hollow cylindrical externally threaded screw, and the sleeve-is provided with a knurled head 23, by means-of which the sleeve may be adjusted in position with respect to the plunger 19 and and the lower supporting'member 2 1 of magnetic material. A closing or operating air gap 25 is provided between the upper and en larged end of the plunger 19 and the upper member 26 of the magnetic structure of the switch. A holding or holding-open air gap 27 (Fig. 3) is provided between the upper portion of the plunger 19 and the adjustable sleeve 22 of magnetic material. The lower end 20 of the plunger 19, which is of reduced cross-section, is adapted to rest on the support 28 whichis held in position by the two posts 29 and 80. This support 28 arrests the opening movementof the switch and provides a means whereby the closing air gap 25 may be adjusted if desired. The plunger 19 will rest on this support if the switch windingsv are deenergized, if the series'winding 31 which surrounds a portion of the plunger 19 and completely surrounds the holding-open gap 27 is energized above the calibrating point or in case the direction of current in the series winding 31 is reversed with respect to theshunt winding To the right of the series coil 31 and. located between the members 24tand- 26 of anaghetie material is the shunt control coil 32. This shunt control cell is-mounted on a core 33 of magnetic material and is clamped between the members 21- and 26 by means of the bolt 34-.

A magnetic blow-out device comprising the plates 35 and 36 which are respectively connected to the strips 37 and' '38 of mag netic material which shunt the closing gap The are chute 39 of magnetic material is held bet-ween the two plates 35 and 36 in such a position that the arcs caused by thev opening of the switch contacts 1 1 and 17 will be disrupted due to the magnetic distortion set up by the fluxacross the plates 35 and 36. This improved mag netic blowout device is the invention of Eugene H. Carichoi'l, one of the present joint applicants, and is fully described and claimed in a co-pending application, Serial No. 421,212, filed November 2, ;1920. This application is assigned to the same as si nee as the said co-pending' application or Eugene R. Caricholt.

The operation of our invention will be understood from adescription of Fig. 4 taken in connection with the other three figures. Referring to Fig. 4, the electric motor having an armature 1O and a shunt field 4:1. is adapted to be connected to the source of supply 412, alter the disconnecting switch 13 is closed by means of the pilot switch 44; which controls the winding of the line contactor 45. The closing of the line contactor connects the motor armature to the source of supply through the starting resistor 16 and the series winding 31 of our improved electromagnetic switch of the series-lockout type. Our improved switch is used in this arrangement to short circuit the starting resistor when the motor armature current is less than a predetermined valuethe calibrating value of the switch. The shunt winding 32 is energized by the closing of the auxiliary switch 41-7 when the line contactor 15 closes. For purposes of illustration, a specific example will be given. Let it be assumed that the calibrating value of the switch is 100 am peres and that the ciiirrent in the motor 1'- mature circuit is in excess of 100 amperes. The flux set up by the shunt controlling coil 32 is substantially constant, and because of the fact that the end 20 of the plunger 19 is magnetically saturated, the magnetic flux will be forced to pass across the holdingopen gap 27 and cause a torque to be set up on the bell crank lever 11 which opposes the torque set up by the flux across the closing gap 25 to such'an extent that the switch will be magnetically locked open. 13y reason of the tact that'the lower end 20 of the plunger 19 is saturated. the flux set up by the shunt winding 32, which is in the same direction as the flux set up by the series coil 31, will distribute itself substantially equally across the ;holding-open gap-27 and the closing gap 25, so that the shunt winding has substantially no influence on the holdingopeneffect of the contractor. In case the current in the series winding 31 is reduced due to the speeding up of the motor, and the cur-rent is less than 100 amperes, the calibrating value, the flux across the hold-- ing-open gap 27 will be reduced to such a value that the torque set up by the flux across the closing gap 25 will cause the plunger 19 to be attracted to the magnetic member 26. The bell crank lever 11 will thereby be turned counter-clockwise and the movable switch contact will be caused to make engagement with the stationary contact 17 and thereby short circuit the resistor 46 in the motor armature circuit. When the current in the series winding 31 is at any value below 100 amperes, the calibrating value, the flux set up by the shunt controlling coil 32 superposed upon the flux set up by the series coil will cause the switch to close. That is because of the fact that these two fluxes are insufficient to cause sufficient flux to pass across the holding-open gap 27 to exert sufficient torque to hold the switch in the open position. In other words, with any value of series current below the calibrating value the shunt controlling coil insures that there will always be a sufficient torque set up by the pull across the closing gap 25 to insure the closing of the switch.

a By reason of the position of the shunt coil 32 in the magnetic circuits and by reason of its location with respect to the closing? gap 25, the shunt coil will of itself cause the switch to close when theampere turns of the coil 32 are sufficient to set up sufficient magnetic flux through the magnetic structure. In other words, if the series winding 31 were deenergized, the flux set up by the shunt winding 32 would cause the switch to close, but the shunt winding of itself has no effect in magnetically holding the switch member in the open position. The series winding of itself, with or without the shunt winding, will cause the switch to be magnetically locked open if the current through the series windingis in excess of the calibrating value of the switch. With only the series winding energized, the switch will not close below a certain value. In the particular type of switch which we have selected for purposes of disclosing our invention, this value of current is approxi-' niately 30 per cent of the calibrating value. Below this 30 per cent, the torque set up by the pull across the closing gap 25 is insufficient to counteract the effect of gravity tending to hold the switch in the open position. In case the series winding alone is used and the load on the motor at starting is of such value that the motor armature current is less than 30 amperes, the resistor 46 would remain in the motor armature circuit. If the load on the motor should then be suddenly increased, the motor speed would drop very materially due to the volt-age drop across the resistor a6, and when the switch operates to short circuit the resistor, the motor speed.

would again increase. Such fluctuation in the motor speed is undesirable, and our invention provides means whereby the armature resistance 46 is short circuited at all times when the load on the motor is less than the calibrating value of the switch. The flux set up by the shunt controlling coil 32 is in such a direction that it normally assists the flux set up by the series coil 31 and, as before stated, by reason of the relative positions of the two coils and the arrangement of the magnetic circuits, and also from the fact that thereis a certainamount of the fluxes set up by the two windings which are leakage fluxes, the shunt coil 'will have no effect in magnetically holding the switch open, but will have a constant tendacross the closing gap 25 is insufficient to operate the switch against the force of gravity and .the friction of the various parts, the flux due to the shunt coil 32 will exert sufficient pull across the closing gap to close the switch. The switch will therefore close at all values below this 30 amperes as well as all values above 30 vamperes up to 100 amperes, the calibrating value.

Another important feature of our invention is that of its use as a reverse. current protective device. If the direction of current through the motor armature circuit is reversed due to. any of the well known causes, the direction of current through the series winding 31 is accordingly reversed. a

This will set up a flux which will act in opposition to the flux set up by the shunt coil 32 and at a certain value of the current in the series coil, the flux passing acrossv the closing gap 25 will be insufficient to counteract the effect of the pull across the holding open gap, the effect of gravity and the spring pressure of the contacts so as to hold the switch in the closed position. The switch will therefore open. It will not reclose at any value within the operating range of the switch, for the reason that the fluxes set up by the shunt coil andthe series coil act in opposition at the closing gap 25, and the leakage fluxes of the two coils are thereby increased to: such.- an extent that there will never be a sufficient flux across the closing gap which will be ef fective in opposition to the'fiux across the holding open gap in causing the switch to close. Reverse current protective devices have heretofore had the disadvantage that although they will open in responseto a reverse current, they will nevertheless reclose in case the reverse current is in excess of a certain value. Vith ourimproved elec tromagnetic switch, no amount of reverse current within the operating limits of the the magnetic forces of the switch tending to move the s itch from, the open position to the closed position and to hold the switch in the open position are given in Fig. 5. These curves show the magnetic forces exerted on the core or plunger 19 with 'the bell cranl'; switch member 11 removed.

The curves have been taken in this manner for the reason that it is believed that the principles of the invention will be bettei understood. It will be observed from tln. curve A, which represents the magnetic forces set up when the series: coil 31 alone is energized. that the loch-out setting oi this coil is 100 per cent of the assumed full load current of the motor, and that the core 19 will b held in its lower position at all values of current above this 100 per cent, but that the core will be caused to move to its upper position at values of current be tween this 100 per cent and 20 per cent or" the full load current. The weight of the bell crank lever 11 and the parts associated with the movable switch contact ll will be such that ordinarily the switch will not close at a value of less than 30 per cent of the calibrating value of the switch wherethe series coil alone is energized. From the curve B it is seen that the core 19 will be caused to move to its upper position at all values of current in the series coil 31 below the 100 per cent full load current when the shunt coil is energised. It is believed that with this brief explanation and with the explanatory matter given. with the d rawing, the curves will be readily understood by those skilled in the art. it will be obvious to those skilled in the art that. while we have illustrated and described our invention in connection with. an. electromagnetic switch. the invention is not necessarily limited to its use in this connection, since an electroman; netic switch is merely one form of an electromagnetic device.

In accordance. with the provisions of the patent statutes, we have described the principle of operation of our invention, together with the apparatus which we now consider to represent the best embodiment thereof, but we desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means What we claim as new and desire to secure by Letters Patent of the United States, is

1. An electromagnetic device comprising .1 magnetic opera-ting member, an operating electromagnet therefor having a magnetic structure and an energizing winding for magnetically holding the said member in one position when the current in the said vinding is above a predetermined value and for magnetically moving the said member to a second position when the current in the said winding drops to said value. and means for insuring the movement of the member to the second position at all values of current in the said winding below said predetermined value.

2. An electromagnetic device comprising an operating member normally biased to one position, an electromagnet having; a winding for magnetically holding the member in that position when the current in the said winding is above a certain value andior magnetically operating it to a second position and holding the same in the second position magnetically when the current in the said winding is within a range of values less than the certain 'value, and means for insuringthe operation of the member to the second position at all values of current in the said winding up to the said range of values.

3. An electromagnetic device comprising an operating member normally biased to one position, an electromagnet having a winding for magnetically holding the said member in that position when the current in the-said winding is above a certain value and for magnetically operating; the said member to a second position and holding the same in the second position magnetically when the current in the said winding is within range of values less than the certain value, and means supplementing the effect of the windingoi? the said electromagnet for insuring the operation of the said member to the second position at all values of current in the said winding up to the said range of values.

i. An electromagnetic device comprising a magnetic operating member, an operating olectromagrnet therefor having a winding and amagnetic structure energizedthereby wnich magnetically holds the said member in one position when the current in the said magnet winding is above a predetermined value and which magnetically moves the member to' a second position when the cur rent in the said winding drops to said value, and means for setting up a substantially constant magnetic flux in the said magnetic structure for insuring the movement of the said member to the secondposition at'all values of current in the said winding below said predetermined value.

5. An electromagnetic device comprising a magnetic movable member, an electromagnet having one winding: which when alone energized will operate the said member, and a second winding which when energized above a certain value simultaneously with by a variable current and a substantially constant current which supplements the effect of the variable current, for setting up two magnetic forces with respect to thesaid member, one for moving the said member to another position and the other for holding it in the biased position. the said holding force predominating at all values'ot the variable current above a predetermined value and the said moving force predominating within a range of values of the variable current less than the said predetermined value, the supplementing effect of the constant current insuring the movement of the said member at all values of the variable current less than the said range of values.

7. An electromagnetic device comprising an operating member normally biased to one position, an electromagnet for holding the same in a second position, means whereby the magnet holds the said member in the first position when the current in the magnet winding is relatively high and permits itto move to the second position when the current is less than a predetermined value, and acontrolling winding on the electromagnet which exerts substantially no effect in holding the member in the first position but insures the operation of the same to the second position when the current in the first winding is at any value below the predetermined value.

8. The combination in an electromagnetic device of the lock-out type, of an operating member, an electromagnet having a variable current winding which operates to magnetically hold the member in one position when the current in the said winding is above a certain value and to magnetically operate the member to a second position and magnetically hold the same in the second position when the current in the said winding is below the certain value, and a winding cooperating with the said variable current winding for insuring that the member will be positively moved to the second position at all values of current in the variable current winding below the certain value.

9. An electromagnetic device comprising a winding carrying a variable current and a. winding carrying a substantially constant current, a magnetic structure for the windings having a movable member acted upon by the combined flux set up by the windings to hold the member in one position when the current in the variable current winding is above a certain value and to move the member to a second position at all values of current in the variable current winding below the certain value.

10. An electromagnetic device of the lockout type comprising an electromagnet having a variable current winding, a movable switch operating member biased to a position between two air gaps, one of which is an operating gap and the other of which is a holding gap, and a constant current winding cooperating with the variable current winding across the operating gap for cans-- ing the said member to move to another position against its bias at all values of current in the variable current winding below '1 predetermined value.

11. An electromagnetic device of the lock-out type comprising an electromagnet having a magnetic structure with a movable switch operating member biased to an open position of the switch and positioned between two air gaps, oneof which is a closing gap and the other of which is a holdingopen gap, a variable current winding surrounding the holding-open gap, and a constant current winding disposed on the magnetic structure parallel with the movable operating member for causing the operating member to close the switch at all values of current in the variable current winding below a predetermined value.v

12. An electromagnetic device comprising an operating member biased to one position, a magnet winding therefor, means 1 whereby the member is magnetically held in another position against its bias to the first position when the current in the said winding is in one direction, and the member is returned to its biased position when the current in the Winding is reversed and magnetically held in the biased position as long as the reverse current persists.

13. An electromagnetic device having a variable current winding a magnetic movable switch operating member biased to one position, and a constant current winding, and means whereby the said member is magnetically operated to a second position and magnetically maintained in the operated position when the effect of one winding supplements the effect of the other winding and the said member is returned to the biased position and magnetically held in the biased position when the wind- 12-0 ings act differentially with respect to each other.

14; An electromagnetic device having a variable current winding and a constant current winding, a movable magnetic member biased to one position, and a magnetic structure energized by the said windings to set up one magnetic force to operate the said member to a second position and magnetieally maintain the member in the operated position when the effect of the variable current winding supplements the effect of the constant current winding and another predominating magnetic force to return the said member to the biased position and magnetically hold the same therein when the variable current winding acts differentially with respect to the constant current winding.

15. A reverse current protective device comprising an electromagnetic device having a movable switch operating member normally in a biased position, a variable current winding and a constant current winding acting jointly therewith to cause the said member to be moved to and magnetically held in another position and acting differentially therewith in response to a reversal of current in the variable current winding to permit the said member to return to the biased position, and means whereby the said member is held in the biasedposition long as the windings have a differential action.

16. An electromagnetic device having a series winding and a shunt winding, a switch operating member normally biased to one position controlled thereby, and a magnetic structure for the windings constructed and arranged so as to cause the said member to be operated to and mag-.

the biased osition as 1on as the current inthe series winding. is in the reverse direction.

17 An electromagnetic device of the look-out type comprising a magnetic structure, a switch operating member normally biased to the open position of the switch and positioned between two air gaps, one of which is a closing gap and the other of which is a holding-open gap, a series winding and a shunt winding disposed on the magnetic structure cooperating to operate the said member to close the switch and hold the switch closed magnetically, and acting differentially with respect to each other in response to a reversal of current in the series winding to permit the said member to open the switch and to magnetically hold the switch in the open position as long as the current in the series winding is in the reverse direction.

In witness whereof, we have hereunto set our hands this first day of November, 1920.

EUGENE R. CARICHOFF. BENJAMIN JONES. 

